Japanese Patent Laid Open No. 2004-116398, for example, discloses information on a conventional internal combustion engine adapted to be operable with gasoline and hydrogen as its fuels. In this internal combustion engine, a hydrogen adding rate is determined for reduced NOx emissions, and the gasoline and the hydrogen are injected at the adding rate.
Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention.
[Patent Document 1] Japanese Patent Laid Open No.